In Greek mythology, Idas was a son of Aphareus and Arene and brother of Lynceus. He and Lynceus loved Hilaeira and Phoebe and fought with their rival suitors, Castor and Polydeuces, killing the mortal brother Castor. He was also one of the Argonauts and a participant in the hunt for the Calydonian Boar. He kidnapped Marpessa. Apollo also desired her and Zeus made the girl choose. She chose the mortal Idas, fearing that Apollo could abandon her when she grew old. With Marpessa, Idas had one daughter named Cleopatra.